1. Field of the Invention
The present invention relates to a high-frequency module that includes a module substrate on which a filter component is mounted.
2. Description of the Related Art
To date, high-frequency modules have been proposed that include a module substrate on which a filter component is mounted. A filter component having a chip size package (CSP) structure that includes a filter substrate that includes a plurality of resonators, which define a filter, provided on one main surface thereof and a package substrate on which the filter substrate is mounted; and a filter component having a wafer level chip size package (WL-CSP) structure in which a filter substrate on which a filter is provided is directly mounted on a module substrate have been proposed as examples of such a filter component that is mounted on a module substrate.
Furthermore, in such a filter component, generally, an inductor is mounted that is for adjusting the characteristics of a filter that is formed of resonators that utilize elastic waves. For example, in a CSP-structure filter component, as illustrated in FIG. 7, inductors La and Lb are provided in a package substrate 500. The package substrate 500 is formed by stacking a plurality of insulating layers 501 to 504 on top of one another and a filter substrate (not illustrated) is mounted in an area 505 enclosed by a dotted line on one main surface of the insulating layer 504. In addition, first and second terminals 506 and 507, through which an RF signal is input and output to and from a module substrate on which the filter component is mounted, and third terminals 508 that are connected to ground electrodes of the module substrate are formed on the other main surface of the insulating layer 501.
Furthermore, in the example illustrated in FIG. 7, a plurality of series-arm resonators that are arranged in a series arm connected between input/output terminals of the filter and two parallel arm resonators, one end of each of which is connected to the series arm, are formed on the filter substrate. The input/output terminals of the filter are connected to wiring electrodes 509 and 510, which are for extracting an RF signal, and are connected to the first and second terminals 506 and 507 via interlayer connection conductors 511.
In addition, the other end of one of the parallel arm resonators is connected to a ground wiring electrode 512 that is formed on the one main surface of the insulating layer 504, and is connected, via interlayer connection conductors 513, to a wiring electrode 514 that is formed on one main surface of the insulating layer 503 and forms the inductor La, to a ground wiring electrode 515 that is formed on one main surface of the insulating layer 502, and to the third terminal 508. Furthermore, the other end of the other parallel arm resonator is connected to a ground wiring electrode 516 that is formed on the one main surface of the insulating layer 504 and is connected, via interlayer connection conductors 517, to a wiring electrode 518 that is formed on the one main surface of the insulating layer 503 and forms the inductor Lb, to the wiring electrode 515, and to the third terminal 508.
The inductor characteristics of the inductors La and Lb can be adjusted by changing the pattern shapes, the line lengths and the thicknesses of the wiring electrodes 514 and 518.
In the example illustrated in FIG. 7, the inductors La and Lb, which adjust the characteristics of the filter, are arranged inside the package substrate 500 of the filter component. Consequently, there is a problem in that the insulating layer 503 is necessary for arranging the wiring electrodes 514 and 518 that form the inductors La and Lb and the thickness of the filter component (package substrate 500) mounted on the module substrate is increased.
Furthermore, if the line lengths of the wiring electrodes 514 and 518, which are for forming the inductors La and Lb, are increased and another wiring electrode is additionally formed in order to form another characteristics-adjusting inductor without increasing the size of the package substrate 500 so as to not increase the size of the filter component, there is a risk that the following problem will occur. That is, the wiring density, inside the package substrate 500, of the wiring electrodes 514 and 518, which are for forming the characteristics-adjusting inductors La and Lb, is increased and the wiring electrodes 514 and 518 are arranged closer to each other.
Therefore, the wiring electrodes 514 and 518 electromagnetic-field couple with each other and, for example, an unwanted capacitance component is generated therebetween and consequently, there is a risk that the attenuation characteristics of the filter will vary. In addition, since the space in which to arrange the wiring electrodes 514 and 518 for forming the inductors La and Lb inside the package substrate 500 is limited, there is a problem in that it is difficult to adjust the attenuation characteristics of the filter by adjusting the inductance values of the inductors La and Lb by changing the pattern shapes, the line lengths and the thicknesses of the inductors La and Lb.